Diamond-tiled workpiece for durable surfaces

ABSTRACT

A method for producing a durable, non-stick, diamond-tiled implement and the diamond-tiled implement thereby produced. Diamond particles are distributed on a surface of a workpiece containing a ceramic binder. The ceramic binder on the surface of the workpiece is heated to above its glass temperature to fuse the diamond particles in and onto the workpiece. The workpiece is then cooled so that the diamond particles are bonded to and at least partially embedded in the ceramic binder at the surface of the workpiece to produce durable, non-stick, diamond-tiled implements including cookware, bakeware, hot-presses, ski surfaces, skid surfaces, marine articles, and mechanical polishing wheels. Other implements of this invention utilize a high diamond content to produce thermally conducting and electrically insulating coatings for heat spreaders, or conversely, heaters.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 USC § 119 to U.S.provisional patent application Ser. No. 60/090,700 filed Jun. 24, 1998,the entire contents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to both a method for producing a durablenon-stick workpiece article and the article of manufacture produced bythe inventive method.

[0004] More particularly, this invention relates to the consolidation ofdiamond powder to a binder coating the surface of a metal substrate.

[0005] 2. Discussion of the Background

[0006] Non-stick articles are quite prevalent in today's world.Polytetrafluoroethylene (TEFLON) is one material that is widely-used formany non-stick applications. Besides TEFLON, silicone coatings are alsoused in non-stick applications. Both TEFLON and silicone, however, arevery soft materials and suffer from abrasive wear which shortens thelifetime of the non-stick article. In addition, TEFLON and silicone haverelatively low temperature ratings. For example, when a TEFLON coatingbecomes too hot, the TEFLON begins to decompose spontaneously.

[0007] Porcelain enameling is a commercial, industrial scale technologywhich is used to coat a variety of objects of various sizes and shapes.Porcelain by itself can provide a smooth, stick resistant surface. Theuses of porcelain enameling include glass-lined water heater tanks,cookware, kitchen appliances, barbeques, heat exchangers, architecturalpanels. decorative jewelry, road signs, and silo panels used for grainstorage. Porcelain enamel is used as a protective coating on a varietyof metals and is used as a glazing on glassware and whiteware.

[0008] The porcelain coating industry for years has developedappropriate enamels for various base substrate materials. The porcelaincoating industry relies heavily on experiential data to obtain the bestenamel coating and adhesion to the wide variety of metals which itcoats. The methods used to coat aluminum with porcelain are differentthan the methods used to coat steel with porcelain. Likewise, methodsfor coating low-carbon steel are different than methods for coating castiron, and methods for coating copper and gold are different from methodsfor coating steel formulas. Methods of applying a porcelain coat tometal typically include the application of ground coats (also calledbase coats). Also, these methods typically contain top coats which willcontrol the background color and finish of the coated workpiece;however, porcelain surfaces are prone to scratching, particularly whenbeing cleaned with an abrasive.

[0009] Diamond, due to its low coefficient of friction and highhardness, is an excellent non-stick material; however, high-pressure,high-temperature (HPHT) synthesis of diamond on common metal and glasssurfaces is not possible because the temperatures attained during HPHTsynthesis exceed the melting points of many common metals and glasses.Further, HPHT synthesis is only practical for limited areas because ofthe high pressures (100 GPa) required for HPHT synthesis.

[0010] Diamond is known to have many superior properties when comparedto other materials. These properties make diamond a viable candidate forapplications where the surface of a material is exposed to mechanical,chemical, or physical wear. For example diamond is known to have a lowcoefficient of friction and superior hardness. As such, diamond would bean ideal candidate for non-stick surfaces and could potentially replaceTEFLON coatings on cooking surfaces. Diamond is also known to have lowsputter yield and is extremely chemically resistant. As such, diamondwould be an excellent protective coating on electrodes and surfacesexposed to plasmas and ion bombardment. Diamond's superior chemicalresistance would make it an ideal container coating in applicationswhere leaching of the wall materials by the chemical effluent eitherproduces contamination of the process stream or produces a long-termreliability problem for the storage of the effluent.

[0011] Unfortunately, the application of diamond directly to typicalsurfaces presents high technical and cost barriers which have eithermade diamond application impossible or extremely costly. On the onehand, high pressure synthesis is used to produce nearly 100 tons ofsynthetic grit per year at a fairly cheap cost per carat (currentselling prices are under $1.00/carat). The high temperatures andpressures required for high pressure synthesis of diamond are notcompatible with coating diamond directly onto common materials such assteels, aluminum, or glassy materials. On the other hand, chemical vapordeposition (CVD) of diamond is a viable technical approach for theformation of diamond on these common materials. Indeed, deposition onthese materials directly or with the use of surface pre-treatments orinter-layers has been demonstrated. U.S. Pat. No. 5,686,152 to Johnsonet. al. teaches a method using electrical bias to directly nucleate andgrow diamond films on substrates using a CVD approach wherein anelectrical bias is applied to the substrate to enhance nucleation.Unfortunately, the high cost of CVD diamond ($5-$20/carat) restrictsthis approach.

[0012] Chemical vapor deposition (CVD) of diamond can be conducted atatmospheric pressures. However, industrial economies of scale cannot berealized with the manufacturing equipment currently available to producelarge area CVD coatings. As a result, large area CVD coatings of diamondare too costly for manufacturers to feasibly employ.

[0013] U.S. Pat. No. 3,338,732 to Holcomb teaches a method of embeddingsilica particles in a porcelain enamel to give the porcelain enamel arough appearance. A porcelain ground coat is applied to a metalsubstrate and heated so that the porcelain ground coat becomes fused tothe metal substrate. Next, a wet cover coat of porcelain enamel isapplied to the ground coat by spraying or dipping. While the cover coatis still wet, silica particles are sprinkled over the wet cover coat sothat the silica particles become partially embedded in the wet covercoat. The cover coat is heated to fuse the cover coat to the ground coatand to fuse the silica particles to the cover coat. Next, a top coat isapplied to the exposed portions of the cover coat and the silicaparticles. The top coat is then heated to fuse the top coat to theexposed portions of the cover coat and the silica particles. Theresulting product has a rough surface on which there is no exposedsilica.

[0014] U.S. Pat. No. 3,650,714 to Farkas discloses a method of coatingsingle diamond chips with titanium or zirconium. The diamond chips arerelatively large, having a mesh size of 200-250. Farkas teachesoverlaying the titanium-coated diamonds with a second layer of nickel orcopper or both nickel and copper, placing the coated diamonds on a steelsubstrate, and covering the coated diamonds with powdered ceramic. Thepowdered ceramic is then vitrified to secure the coated diamonds to thesteel substrate. Since the diamond chips are coated, no portion of thesurface of the diamonds is exposed and the diamonds are not bonded tothe ceramic.

[0015] U.S. Pat. No. 4,749,594 to Malikowski et al. discloses a methodfor coating ceramic surfaces with hard substances. The method includesthe steps of coating a metal or ceramic substrate with a metal powder,the spraying the substrate with a diamond powder, and heating the coatedsubstrate to between 900 and 1200° C. The heating step causes the metalpowder to melt. The molten metal wets both the diamond particles and thesubstrate. When the melted metal is cooled, diamond particles from thediamond powder are integrally bonded to the substrate by the formedsolder (hardened metal). The step of heating the coated substrate isperformed in a high purity argon atmosphere or at sub-atmosphericpressure to prevent reactions between the active component of the metalpowder and the remaining gases. In a first example, the invention ispracticed with 40-50 micron diamond powder; in a second example, theinvention is practiced with 60-80 micron diamond powder.

[0016] U.S. Pat. Nos. 5,164,220 and 5,227,940 to Caballero disclose amethod of coating a metal substrate with treated diamond particles.Chemical plasma deposition is performed to grow an SiC crystal layer onthe diamonds. Caballero discloses several different techniques forcoating the metal substrate with the treated diamond particles. Thesetechniques include sintering, brazing, and electroplating.

[0017] U.S. Pat. No. 5,453,303 to Holcombe et al. teaches a method ofdepositing a full diamond coating on a substrate. A powder mixture ofglassy carbon and diamond particles is heated and impinged upon thesubstrate at high velocity. Upon impact with the substrate, the glassycarbon is phase transformed to diamond. The diamond particles promotethe phase transformation of the glassy carbon to diamond. Similarly,U.S. Pat. No. 5,635,254 to Holcombe et al. teaches a method ofdepositing a layer of diamond or diamond-like material on a substrate.In one embodiment, a plasma gas stream heats and propels a mixture ofglassy carbon and diamond particles onto the substrate. The mixture isthen quenched on the surface of the substrate to produce a diamondcoating.

SUMMARY OF INVENTION

[0018] Accordingly, it is an object of the present invention to takeadvantage of the durability and non-stick characteristics of diamond inproviding a novel durable, non-stick workpiece at relatively low cost.

[0019] It is also an object of the present invention to provide a novelmethod of manufacturing a durable, non-stick workpiece in whichdurability and non-stick characteristics are achieved by use of diamond.

[0020] It is also an object of the present invention to provide a methodfor producing a diamond-tiled, durable, non-stick surface on a varietyof objects having various, shapes, sizes and surface areas.

[0021] It is also an object of the present invention to provide anarticle of manufacture having a durable, non-stick, diamond-tiledsurface.

[0022] These and other objects of the present invention are achievedaccording to a novel method of producing a diamond coated implementwherein a workpiece having a surface including a ceramic binder isprovided. Diamond particles are distributed on the surface of aworkpiece. The surface is heated to melt at least a portion of theceramic binder. Then the surface of the workpiece is cooled so that aportion of the diamond particles remain bonded to, and embedded in, theceramic binder at an exposed surface of the workpiece to produce adiamond-tiled coating layer. Optionally, a ceramic binder may bedistributed on the workpiece as a dry powder frit, eliminating the needto provide a workpiece having a surface that includes a ceramic binder.

[0023] According to the novel method of the present invention, adurable, non-stick, diamond-tiled surface coating is provided on theworkpiece (i.e. the surface is diamond-tiled). The inclusion of diamondpowders in the surface of the workpiece causes the durability of theworkpiece to surpass the durability of conventional workpieces that arecoated with TEFLON or with porcelain alone. The diamond coated surfaceis resilient to high temperatures and resistant to abrasion.

BRIEF DESCRIPTION OF DRAWINGS

[0024] A more complete appreciation of the invention will be obtained asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings, wherein:

[0025]FIG. 1 is a flowchart describing the method of forming adiamond-tiled surface in accordance with the teachings of the presentinvention;

[0026] FIGS. 2(a) through 2(e) are sectional views of a workpiece atvarious processing steps when using a fired porcelain ceramic surface asthe starting workpiece;

[0027] FIGS. 3(a) through 3(e) are sectional views of a workpiece atvarious processing steps when using porcelain frit and diamond powder tocoat a porcelain ceramic workpiece; and

[0028] FIGS. 4(a) through 4(e) are sectional views of a workpiece atvarious processing steps when using an un-fired porcelain ceramicsurface as the starting workpiece.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Referring now to the drawings, wherein like reference numeralsdesignate identical or corresponding parts throughout the several views,FIG. 1 is a flow chart describing a method of providing a workpiece witha diamond-tiled surface in accordance with the teachings of the presentinvention.

[0030] In step S1, diamond crystallites or a mixture of diamondcrystallites and porcelain frit are distributed evenly over the surfaceof the workpiece. The porcelain surface can be provided on the workpieceusing any appropriate technique known in the porcelain enamel industry.Alternatively, a workpiece that already has a porcelain surface can beused.

[0031] Any suitable technique may be used to distribute the diamondcrystallites or mixture of diamond crystallites and porcelain frit overthe surface of the workpiece. In one embodiment, a suspension of diamondpowder is provided in an aerosol medium. The aerosol is sprayed upon theporcelain surface whereupon the solvent evaporates, leaving behind thedry diamond powder as a top coat. It is important for cost control thatthe aerosol method not use excess diamond powder which will merely addundue cost to the coating process. The porcelain industry currently isdeveloping solvent-less electrostatic spray techniques used quitecommonly now in the paint industry to restrict volatile organic compound(VOC) emissions. These techniques are very efficient with little paintpigment loss. These electrostatic spray techniques may be used toprovide a very precise and controlled method for uniformly dispensingdiamond powder onto the porcelain surface. These simple spray techniqueslend themselves to patterning of the diamond on the workpiece surfaces.

[0032] Any diamond powder can be used to provide the diamondcrystallites used for the invention. For applications as a diamond-tiledcookware surface, the powder is graded to a size that is less than 5microns in diameter. That is, the powder is sieved such that most, ifnot all, of the particles having a maximum diameter of more than 5microns are removed. In the context of the present invention, the“maximum dimension,” the “particle size,” and the “powder size” of thediamond particles all refer to the size to which diamond powder has beengraded.

[0033] Powder sizes greater than 5 microns in diameter will result inthe diamond-coated surface having a rough surface finish. This willrequire additional measures to finish the coated surface. By usingpowder size less than 5 microns in diameter, the surface roughness willbe approximate to standard industrial finishes. Smaller powder size willalso help in suspension of the powder and its dispersion over theworkpiece surface. For other applications, the crystallite size chosenwill be dependent on nature of the application. In fluid handlingapplications, the crystallite size will determine the surface roughnessand thus the viscosity of the fluid along the container boundary. Here,a rough surface is desirable. It creates slip planes in the fluid whichreduces the frictional drag from the walls. If the diamond coatedsurface is applied to a polishing or finishing wheel, small powder sizespermit polishing operations while very small powder sizes permitfinishing operations. If the diamond coated surface is applied to alapping wheel, larger powder sizes are desirable for performing grindingand lapping operations.

[0034] Diamonds of any size may be used to implement the teachings ofthe present invention. For example, large diamond particles (e.g.,diamond particles having a maximum dimension greater than 50 microns)may be used in decorative applications including the adornment ofchinaware or jewelry.

[0035] In step S2, the workpiece having the diamond-tiled coating isfired to above the glass temperature of the particular porcelain enamelused. For aluminum-based porcelain coated materials, the glasstemperature of the porcelain is typically ranges from 500 to 600° C. Forsteel-based porcelain coated materials, the glass temperature of theporcelain is typically ranges from 650 to 850° C. At these temperatures,the porcelain glass surface becomes fluid. The diamond powder, whichstill remains far below its melting temperature, penetrates the fluidsurface of the porcelain.

[0036] In some applications, it is desirable to spray dry diamond powderdirectly onto the porcelain glass while in the high-temperature fluidstate, i.e., after the porcelain has been heated. When the porcelain isheated before the distribution of diamond powder, it may be desirable toheat the porcelain again after the distribution of diamond particles. Ifan aerosol medium is sprayed directly onto fluid porcelain glass, theaerosol medium is preferably non-explosive to eliminate the risk ofexplosion.

[0037] Diamond attachment to the porcelain surface occurs as a result ofchemical and mechanical bonding between the diamond crystallites and theporcelain enamel glass. During the high-temperature firing process, itis observed that the fluid porcelain glass wets the diamond surface.Wetting of one surface by another is evidence of the formation of achemical bond at the interface between the two materials (the amorphousglass and the crystalline diamond). Furthermore, the expansioncoefficient difference between diamond (1 ppm) and the porcelain glass(5-10 ppm) results in compression forces on each of the diamond powdercrystallites as the porcelain surface cools below the glass temperatureof the porcelain (approximately 550° C., depending on the type ofporcelain). These forces serve to embed the diamond crystallites ontothe porcelain surface under a compressive stress which adds a mechanicalbond.

[0038] Once the diamond surface penetration is complete, the workpieceis cooled to below the glass temperature of the porcelain in step S3 sothat the porcelain hardens. As the porcelain hardens, compressivestresses develop on the diamond crystallites which serve to fix thediamond crystallites onto the porcelain surface. The cooling ramp toroom temperature is best dictated by procedures and practices used inthe porcelain industry to prevent spalling of the porcelain enamelcoatings.

[0039] Residual un-reacted crystallites are removed from the surface instep S4. Preferably, water with an abrasive action is used in step S4 toremove the residual powder. The residual diamond crystallites go intosuspension in the water and are rinsed from the surface. The water maybe captured and evaporated, leaving behind the un-reacted diamondcrystallites. Thus, the un-reacted crystallites are reclaimed for futureapplication.

[0040] Diamond surface exposure must be insured if the inherentproperties of the diamond are to be realized. For many applications, itis desirable to have a diamond surface exposure percentage thatmaximizes the lifetime of the workpiece. The diamond surface exposurepercentage depends, in part, on the firing conditions and the particlesize of the diamond crystallites. For example, the use of extremelycoarse powder (e.g., particles having a maximum diameter of at least 10microns) and short firing times will not permit complete encapsulationof the diamond powder by the porcelain enamel glass. On the other hand,the use of very fine diamond powder (e.g., particles having a maximumdiameter less than or equal to 0.1 microns) and long firing times, e.g.,four minutes, may result in complete encapsulation of the diamondcrystallites in the porcelain glass. In this case, post-firing processessuch as mechanical polishing, chemical etching, chemi-mechanicalpolishing, or reactive ion etching may be used to expose the diamondsurfaces. The density of diamond powder at the surface must be a highpercentage for the properties of diamond to dictate the performance ofthe diamond/porcelain composite. The diamond powder may be layered onthe surface of the porcelain glass; the layering determines the maximumdensity of diamond powder obtainable on the unfired surface.

[0041] Standard formulae depending on the shape and packing structurewill then determine the diamond powder density on the surface. For asingle-size spherical particle and a close-packed structure, the diamondcrystallites would theoretically occupy 74% of the volume with theremaining volume occupied by air. After firing, the air would bedisplaced by porcelain glass, leaving a diamond/porcelain compositestructure with maximum diamond density of 74%. The top surface of such atheoretical structure would have greater than 78% of its surface diamondexposed. Additional measures known from the composites industry could beutilized (such as mixing of powder sizes) to further increase thevolumetric diamond fraction and thus the diamond surface exposure.

[0042] As a result of performing steps S1 through S4, the diamondcrystallites consolidate onto the workpiece surface with porcelainenamel as the binder. Additional processing may enhance the performanceof the workpiece. Chemical etching may remove some of the porcelainenamel exposing more diamond. For example, a reactive ion etch may beused to etch the porcelain on the exposed surface of the workpiece.Mechanical polishing may also be used to expose more diamond. Plasmaprocessing may be used to chemically etch the diamond producing rounder,slicker edges. CVD processing may be used to consolidate the entiresurface as diamond, e.g., using a CVD diamond applicator as disclosed inU.S. Pat. No. 5,480,686 and in PCT Publication WO 96/41897 (aninternational application published under the Patent Cooperation Treatythat claims benefit of priority from U.S. patent application Ser. No.08/483,982, filed Jun. 7, 1995), both of which are herein incorporatedby reference in their entirety. If CVD processing is performed, theembedded diamond particles provide seed crystals. In any case, thesurface of the diamond is preferably re-hydrogenated in step S5 torestore to the diamond a low coefficient of friction. This isaccomplished simply by polishing the diamond-tiled surface with ahydrocarbon oil-based polish.

[0043] FIGS. 2(a) through 2(e) are sectional schematics of the workpieceat various stages of the process described in FIG. 1. FIG. 2(a) shows asurface of porcelain enamel 1 which has been vitrified from a firingprocess. In this manner, a base substrate 2 in FIG. 2(a) is coated witha highly polished porcelain surface. FIG. 2(b) shows the workpiece afterdiamond crystallites 3 have been uniformly distributed over the surface.FIG. 2(c) shows the workpiece after firing to above the glasstemperature of the porcelain enamel 1. The diamond crystallites 3penetrate into the liquid surface of porcelain while remaining in asolid state. The liquid enamel glass wets the diamond crystallites 3.FIG. 2(d) shows the surface once the glass is cooled to roomtemperature. The diamond crystallites 3 are embedded and embossed on theporcelain enamel surface. As can be seen from FIG. 2(d) some diamondcrystallites 3 a are not attached due to excessive layering of thediamond crystallites 3. The surface is then rinsed and abrasivelyscrubbed to remove the excess un-reacted diamond crystallites 3 a. FIG.2(e) shows schematically the final workpiece after the diamond tilingprocess.

[0044] With the present invention, HPHT synthesized diamond powder (acommercial material with more than 100 tons/year produced) may be tiledonto common metal and glass surfaces using porcelain enamel as the hightemperature binder to secure the individual diamond crystallites to thesurface. Thus, the present invention combines the technology andmaturity of two distinct industrial technologies to enable theproduction of diamond-tiled durable non-stick work-pieces.

[0045] The range of substrates which could be tiled by this process isquite extensive owing to the large number of substrates used in theporcelain enamel industry. These metal substrates include low-carbonsteel, stainless steel, aluminum, cast-iron, copper, silver, and gold.Outside the porcelain enamel industry, whitewares and other hightemperature glasses and ceramics would be quite compatible with thisprocess; for example, CORNINGWARE and other china surfaces which couldbe used as substrates for this process.

[0046] The range of diamond powder sizes which could be used in thisprocess is virtually unlimited, but the preferred range for mostapplications is between 0.01 and 50 microns (i.e., the maximum dimensionof each particle is between 0.01 and 50 microns). If the maximumdiameter of the diamond particles exceeds 5 microns, methods other thansolvents may be implemented to disperse the powder in an efficientmanner. For example, aeration techniques such as those used withsandblasting grit could be used to disperse the diamond particles. Also,the diamond particles could simply be sifted through a screen in orderto disperse the diamond particles. Diamond powder available at extremelysmall sizes (less than 0.1 microns) may be used to implement theinvention. At extremely small sizes, diamond powder tends to cake, andthus, the powder will have to be deflocculated before application to theworkpiece surface. To avoid burning extremely fine diamond powder, careshould be taken in the firing step to avoid oxidizing the diamondpowder. This can be accomplished by either reducing the time at hightemperature, firing at temperatures below 800° C., or restricting theamount of available oxygen.

[0047] The range of porcelain enamel glasses which can be used with thepresent invention is quite extensive. The available range of porcelainsis limited only by the expertise of the porcelain enamel industry indeveloping different porcelains and methods of adhering differentporcelains to base metals. Materials other than porcelain that arecapable of forming strong mechanical or chemical bonds with diamondcrystallites may also be used to bind diamond crystallites toworkpieces; for example, various glasses, whitewares, and ceramics otherthan porcelain may be used as a high temperature binder for the diamondcrystallites.

[0048] The present invention may benefit from the vast knowledge whichhas accumulated from years of industrial practice. Thus, the annealingtimes and cycles will be dependent on the characteristics of the enamelselected by the porcelain industry or other pertinent industries. Forsteel-based enamel coated substrates, relatively higher temperatureenamels that permit temperatures and cycles near 850° C. may beappropriate. For various aluminum alloy-based enamel coated substrates,relatively lower temperature enamels are appropriate so as not to meltthe base substrate; such enamels will be limited to temperatures andcycles near 550 to 600° C.

[0049] Likewise, the atmospheres in the kiln will be determined by theporcelain enamel practice. Experience in the porcelain enamel industryhas shown that humidity should be controlled in the kiln to eliminatecrazing of the enamel finishes. For the practice illustrated in FIGS.2(a) through 2(e), this may not be an extreme issue because the enamelfrit has already been fired by the porcelain manufacturer producing anadherent, glass-protected surface of porcelain enamel 1.

[0050] Another sectional schematic of the workpiece and the process forforming a diamond-tiled workpiece is shown in FIGS. 3(a) through 3(e).FIG. 3(a) shows a surface of porcelain enamel coating a base substrate2. FIG. 3(b) shows the workpiece after porcelain frit 4 and diamondcrystallites 3 have been distributed over the porcelain enamel 1.Diamond powder may be layered on the surface to provide the diamondcrystallites 3. FIG. 3(c) shows the workpiece after firing to above theglass temperature of the porcelain enamel 1. The diamond crystallites 3penetrate into the liquid surface of porcelain enamel 1 while remainingin a solid state. The liquid porcelain enamel 1 is a fluid enamel glassthat wets the diamond powder layers. FIG. 3(d) shows the workpiece oncethe glass (porcelain enamel 1) is cooled to room temperature. Thediamond crystallites 3 are embedded and embossed on the surface ofporcelain enamel 1. As can be seen from FIG. 3(d) some diamondcrystallites 3 a are not attached due to excessive layering of thediamond crystallites. In this case, the surface is then rinsed andabrasively scrubbed to remove the excess un-reacted diamond crystallites3 a. FIG. 3(e) is a sectional view of the final workpiece after thediamond-tiling process.

[0051] Another sectional schematic of the workpiece and the process forforming a diamond-tiled workpiece is shown in FIGS. 4(a) through 4(e).FIG. 4(a) shows an uncoated base substrate 2 made of an un-firedporcelain ceramic. Alternatively, the base substrate 2 may be steel, asteel alloy, aluminum, an aluminum alloy, or any other material on whicha porcelain enamel coat can be formed.

[0052]FIG. 4(b) shows the workpiece after porcelain frit 4 and diamondcrystallites 3 have been distributed over the surface of the basesubstrate 2. Diamond powder may be layered on the surface to provide thediamond crystallites 3.

[0053]FIG. 4(c) shows the workpiece after firing to above the glasstemperature of the porcelain frit 4. The diamond crystallites 3penetrate into the liquid enamel surface while remaining in a solidstate. The fluid enamel porcelain glass wets the diamond powder layers.Preferably, the substrate 2 has a higher melting point than theporcelain frit 4. However, if a laser system or flash annealingtechnique is used to melt the porcelain frit 4, the diamond coated layermay be formed on a substrate 2 having a melting point below the meltingpoint of the frit 4.

[0054]FIG. 4(d) shows the surface once the fluid enamel porcelain glassis cooled to room temperature. The diamond crystallites 3 are embeddedand embossed on the porcelain enamel surface of the workpiece. As can beseen from FIG. 4(d) some diamond crystallites 3 a are not attached dueto excessive layering of the diamond powder. The surface of theworkpiece is then rinsed and abrasively scrubbed to remove the excessun-reacted diamond crystallites 3 a. FIG. 4(e) shows schematically thefinal workpiece after the diamond tiling process.

[0055] A propane-fired kiln may be used in the production ofdiamond-tiled surfaces. Numerous books and technical reports describethe operation, specification, and construction of industrial kilns. Asimple kiln constructed from standard, commercial parts may be used topractice the present invention. At the base of such a kiln is a 20,000BTU propane burner mounted in a cast-iron stand. The cast-iron standalso provides a grate upon which the work-pieces can be set. Forexample, a flat porcelain-coated steel pan, pre-treated with diamondpowder may be placed on the grate. Above the pan is a kiln cover whichprovides thermal insulation forcing a stagnant, non-convecting column ofair to exist above the pan. The kiln cover is further insulated usingaluminum foil to create a high temperature oven. The burner burns astoichiometric mixture of air and propane. The burnt stream of gasdirectly heats the porcelain pan. The temperature of the pan can beobserved by viewing the pan surface by looking through the grate andbeside the propane exhaust.

[0056] Following the firing process, the work-pieces are removed fromthe kiln. Powder which, due to layering, does not react with theporcelain enamel is washed and abrasively scrubbed from the surface. Thediamond embossed surface is then treated with an oil-based polish torestore the surface state of the diamond crystallites to an hydrogenatedstate. An olive-oil polish may be used to restore the hydrogenation ofthe diamond surfaces. Alternatively, the surface of the workpiece may bevacuum fired in order to oxygen denude the surface before exposing thedenuded surface to a variety of hydrogen sources such as atomichydrogen, water, or hydrocarbons.

[0057] A scanning electron microscope (SEM) image of a diamond-tiledworkpiece following diamond consolidation using the method of thisinvention reveals that the porcelain enamel wets to the diamond surfaceand embosses the diamond onto the porcelain surface.

[0058] The process by which the diamond crystallites are fixed on thesurface is a complex process. However, the wetting of the diamondcrystallites by the porcelain glass is itself evidence of a reactivebond occurring between the diamond and the glass. Reactions betweencarbon and silica are well studied reactions and are used quiteprevalently today for the production of silicon carbide abrasivesthrough the following reaction:

SiO ₂ +C (graphite)→SiC+CO (1200° C.)

[0059] Diamond, however, is more stable than graphite, and thetemperatures employed in the present invention are much lower than thetemperatures used in the production of silicon carbide abrasives. Thus,a reaction between diamond and silica in the present invention isremarkable. Such reactions are undoubtedly limited to surface reactionsand can be understood in the light of diamond surface chemistry. Diamondas a hydrogenated surface is a very stable, non-reactive surface.Literature reports that the hydrogenated surface of a diamond gives thediamond its low coefficient of friction. Once the surface becomesdenuded, the coefficient of friction (a measure of the surface'sreactivity) increases. Oxygen terminated surfaces are also fairlyreactive showing a high coefficient of friction. In addition to thesestudies, published work shows the thermal stability of hydrogenated andoxygenated diamond surfaces. It is known that at elevated temperatureshydrogen and oxygen both desorb from the diamond surface. Hydrogendesorbs at 800° C., and oxygen (as CO) desorbs at 600° C.

[0060] The present invention utilizes high temperature surface reactionsto present to the fluid porcelain surface “reactive” diamond surfacesupon which the porcelain can wet. Yet, the temperatures used in thepresent invention remain below values at which there would bespontaneous reaction of the diamond and silica to form bulk SiC and CO.

[0061] A map of the surface carbon (diamond) and surface silicon(porcelain) on the surface of a workpiece treated by the inventivemethod reveals the degree of diamond exposure. One such map revealedthat a diamond exposure of approximately 50% was obtained. Improvementsin dispersion and firing techniques will make possible the production ofsurfaces having a diamond exposure of well over 50%. Also, mechanicaland chemical techniques can be used after firing to expose diamond.

[0062] A Raman spectrum from a workpiece treated by the inventive methodreveals the effect of firing on the diamond powder. The 1332 cm⁻¹ lineof one such Raman spectrum revealed the presence of diamond and showedthat the diamond was neither dissolved by the molten porcelain, burntaway by the firing atmosphere, nor reacted into SiC.

[0063] This invention will be further illustrated by the followingexamples:

EXAMPLE 1

[0064] A diamond-tiled durable workpiece was produced using the processdescribed in FIG. 1 and the simple kiln described above. A porcelainenameled pan was purchased. The pan sold under the trade nameGRANITE-WARE and had a blueish porcelain enamel finish. The bowlcontained a flat bottom. The pan had an outside diameter of 28 cm and aheight of 7 cm. The interior bottom surface of the pan was 13 cm indiameter. Diamond powder screened to powder sizes less than 0.5 micronsin diameter (i.e., the diamond particles had maximum dimensions of lessthan 0.5 microns) were suspended in 120 cubic centimeters of acetone,using agitation to place the powder in suspension. The fluid along withthe suspended diamond powder was placed in a commercial spray gun madeby PREVAL. Then the pan was heated to approximately 35° C. Next, thesuspended acetone/diamond solution was sprayed onto the bottom surfaceof the pan. The acetone quickly evaporated on contact, leaving behind arelatively uniform coating of diamond powder.

[0065] The coated pan was then fired on a kiln resembling the simplekiln described above with the exception that no top cover was used andthe pan was suspended upright above the flame of the propane burner. Thepan was locally heated by the individual pilots on the burner, producinglocal hot regions on the bottom. As these hot spots approachedapproximately 800° C., the diamond powder penetrated the porcelainsurface. The pan was held at 800° C. for approximately 30 seconds. Bymoving the pan around the burner pilots, the bottom surface of theporcelain enameled pan was tiled with diamond.

[0066] The pan was cooled to room temperature, rinsed with water, andabrasively scrubbed to remove any residual diamond powder. The diamondcoverage of the treated area ranged from 50 to 70 percent. The pan wasthen rubbed with olive oil to re-hydrogenate the diamond surface. Thesurface was then wiped dry of excess oil. Scouring the pan withSCOTCHBRITE pads resulted in no visible abrasion of the diamond-tiledsurface.

[0067] Cooking tests were performed. Eggs fried on this surface (usingno cooking oil or spray) readily released from the diamond-tiledsurface. Even those surfaces where the eggs burned against the pan couldbe removed with minimal force under water. To evaluate thestain-resistance of the pan against dry cooking, cooking spray wasapplied to the surface and the surface was cooked until the oil burnedonto the surface producing a dark brown film. Continued heated of thepan merely oxidized away the burnt cooking spray, analogous to aself-cleaning oven interior except that the stains completely atomizednot leaving any coked material.

EXAMPLE 2

[0068] Electric stove top element covers are typically formed ofporcelain enameled steel. A 21 cm diameter element cover was purchasedwith a green enamel color finish. The electric stove top element coverwas diamond powder coated using the same method as used in EXAMPLE 1.The stove top element cover, pre-treated with diamond powder was thenplaced on the grate of a propane-fired kiln similar to the one describedabove. The kiln cover was placed above the kiln. Similar to EXAMPLE 1,the pan was fired to approximately 750° C. The element cover was kept atapproximately 750° C. for about 3 min. The element cover was cooled toroom temperature, had the excess powder removed, and was rehydrogenatedusing the olive oil treatment.

[0069] Visually, the element cover did not show as complete a coverageof diamond powder as the pan in EXAMPLE 1. Nonetheless, cooking testsshowed the surface to be stick resistant and impervious to abrasion bystandard scouring pads used on metal cookware.

EXAMPLE 3

[0070] An electric kiln was used as an alternative to the propane firedkiln used in the previous examples. The electric kiln was calibrated fortemperature and thus provided a more accurate processing environment.The isothermal nature of the commercial electric kiln provided a betterprocessing environment for practice of this invention. The electric kilnused was a Model 145E electric kiln manufactured by Allcraft Tool andSupply, Inc., Hicksville, N.Y.

[0071] Green porcelain enamel soup bowls manufactured by CINSA (soupplate model number 22) were obtained for diamond tiling. The soup bowlswere cleaned using a detergent cleaner, dried on a hot plate, and thencoated with a dry diamond coating using the dispersion and spraypractice used in EXAMPLES 1 and 2. Various bowls were inserted into theelectric kiln at progressively higher temperatures until the temperaturewas sufficient for reaction of the diamond powder with the porcelainenamel. It was found that at temperatures of 670° C. the dry diamondpowder bonded to the porcelain enamel within two minutes. It was thenpossible to re-coat with diamond powder and bond additional diamondpowder onto and in the porcelain enamel surface. After each re-coating,the porcelain surface became whiter in color and mottled.

[0072] One bowl was coated and fired 4 times at 680° C. for 2 minuteseach time. A glass etch (sodium bifluoride) was then used to etch exposethe diamond. The surface, somewhat roughened by the firing treatment,was then polished by hand using progressively higher grades of SiCsandpaper (320, 400, and 600 grades). The resulting polished surface,like those in the previous examples, showed excellent non-stickproperties. After the initial polishing following the etch, the surfaceshowed very little sign of wear by the abrasive papers despite extensiveabrasion. By comparison, the same abrasive paper on untreated bowlsimmediately showed scuffing and scratching on the porcelain glasssurface.

[0073] Additionally, the performance of the bowl to chemical etch by thesodium bifluoride was compared to a standard porcelain enamel bowl. Thestandard bowl was visibly frosted by the glass etch solution. On theother hand, the diamond-tiled bowl made in EXAMPLE 2 was not visiblyfrosted.

EXAMPLE 4

[0074] White porcelain enameled Al pans were obtained from Regal-Ware,Inc. The pans were 25 cm diam pans which had been coated at Regal with˜75 μm of porcelain enamel. Like EXAMPLE 3, an electric kiln Model 145from Allcraft Tool and Supply was used. The pans were sprayed with anaerosol solution similar to that used in EXAMPLES 1 and 2. However, nowa larger diamond powder was used. Diamond powder purchased from theTomei Corporation was used. The powder was graded to a 5-10 μm sizepowder. The aerosol solution consisted of 0.250 gms of diamond powderand 150 ml of acetone. Approximately 35 ml of this solution was aerosolsprayed onto the porcelain coated Al pan, allowing the acetone toevaporate, leaving the dry diamond powder on the surface.

[0075] The pan was placed in the kiln, which had been pre-heated to 500°C. The pan was then heated to 570° C. over a 12 min time frame and thenramped down for 12 min to 500° C. before opening door to kiln andremoving it from the oven.

[0076] The pan like previous examples was very resistant to abrasion astested against various grades of SiC paper (320, 400 and 600 grades).The resultant surfaces were showed good non-stick properties which couldbe improved by buffing with a light oil coat.

COMPARATIVE EXAMPLE

[0077] A light blue plate, precoated with diamond powder, was insertedinto the electric kiln used in EXAMPLE 3. The plate was kept in theelectric kiln for 15 minutes during which time the temperature in thekiln rose from 750 to 950° C. After cooling, the light blue enamel onthe plate had darkened and blistered. No residual diamond powderremained on the surface as in EXAMPLES 1, 2, and 3.

ADDITIONAL APPLICATIONS

[0078] In the above examples, various implements were produced in thepractice of this invention. These implements involved the formation ofdiamond tiled surfaces on plates, bowls, pans, and electric stove topheating elements. Diamond tiled surfaces made in accordance with thepresent invention have many potential uses. Other such implementsinclude cookware; grinding devices; lapping devices; polishing devices;finishing devices: plumbing fixtures including cast iron or steelfixtures having a porcelain coated surface such as bathtubs, toilets,and sinks; skis; skids; heat presses, for example, the type of heatpress used to fuse plastic or cellophane sheets in the manufacture ofplastic or cellophane bags; flatirons; boat hulls and other surfacesexposed to marine environments; electrostatic chucks for handlingsemiconductor wafers; bearings; sliding surfaces of sliding electricalcontacts; and any other application that could benefit from a durable,non-stick surface that is resilient to high temperatures and resistantto abrasion.

[0079] According to the present invention, a diamond-tiled surface canbe formed on a thin porcelain layer. The resultant structure may then belaminated onto a conventional product such as a ski to provide adurable, non-stick (i.e., low coefficient of friction) ski surface.

[0080] In addition, the high diamond content of these surface coatingsmakes these coatings electrically insulating and thermally conductive.Thus, according to the present invention, in a diamond tiled surface canbe formed on top base metals to provide electrical insulation from andthermal conduction to the base metal. Accordingly, metal-based thermalspreaders and electrical resistance heaters can be made with the methodsof this invention. Thus, the present invention has utility in very widefields of application.

[0081] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States:
 1. A method for producing a diamond-tiled workpiece,comprising: providing a workpiece having a surface including a ceramicbinder; distributing diamond particles on the surface; heating thesurface to melt at least a portion of the ceramic binder; and coolingthe heated surface so that diamond particles are bonded to and embeddedin the ceramic binder.
 2. The method of claim 1 , wherein thedistributing step comprises: mixing the diamond particles with avolatile solvent; and spraying mixed diamond particles and volatilesolvent onto the surface of the workpiece.
 3. The method of claim 1 ,wherein the distributing step comprises: electrostatically spraying thesurface of the workpiece with diamond particles.
 4. The method of claim1 , further comprising: partially removing ceramic binder surroundingsaid embedded diamond particles so that at least 40 percent of theexposed surface is diamond.
 5. The method of claim 4 , wherein theremoving step comprises: etching the ceramic binder on the exposedsurface.
 6. The method of claim 4 , wherein the removing step comprises:polishing the exposed surface.
 7. The method of claim 1 , wherein theproviding step comprises: providing a workpiece made of a ceramicmaterial.
 8. The method of claim 1 , wherein the providing stepcomprises: providing a workpiece including a metal substrate and aceramic layer formed on said metal substrate.
 9. The method of claim 1 ,wherein the heating step comprises: heating the surface of the workpieceto a maximum temperature between 500 and 900° C.
 10. The method of claim1 , further comprising: repeating the steps of distributing diamondparticles, heating, and cooling until at least a predeterminedpercentage of the exposed surface is diamond.
 11. The method of claim 1, wherein the distributing step comprises: distributing diamondparticles having a maximum dimension of less than or equal to 50 μm. 12.The method of claim 1 , further comprising: performing chemical vapordeposition to deposit diamond on the exposed surface.
 13. The method ofclaim 1 , further comprising: hydrogenating exposed surfaces of thediamond particles.
 14. The method of claims 1, wherein the providingstep comprises: providing a ceramic binder made of glass.
 15. The methodof claims 1, wherein the providing step comprises: providing a ceramicbinder made of porcelain.
 16. A method for producing a diamond-tiledworkpiece, comprising: providing a workpiece having a surface;distributing a ceramic binder on the surface as a ceramic powder frit:distributing diamond particles on the surface; heating the surface tomelt at least a portion of the ceramic binder; and cooling the heatedsurface so that diamond particles are bonded to and partially embeddedin the ceramic binder at an exposed surface of the workpiece to producea diamond-tiled coating layer.
 17. The method of claim 16 , wherein thedistributing step comprises: mixing the diamond particles with avolatile solvent; and spraying mixed diamond particles and volatilesolvent onto the surface of the workpiece.
 18. The method of claim 16 ,wherein the distributing step comprises: electrostatically spraying thesurface of the workpiece with diamond particles.
 19. The method of claim16 , further comprising: partially removing the ceramic bindersurrounding said embedded diamond particles so that at least 40 percentof the exposed surface is diamond.
 20. The method of claim 19 , whereinthe removing step comprises: etching the ceramic binder on the exposedsurface.
 21. The method of claim 19 , wherein the removing stepcomprises: polishing the exposed surface.
 22. The method of claim 16 ,wherein the providing step comprises: providing a workpiece made of aceramic material.
 23. The method of claim 16 , wherein the providingstep comprises: providing a workpiece including a metal substrate and aceramic layer formed on said metal substrate.
 24. The method of claim 16, wherein the heating step comprises: heating the ceramic binder to amaximum temperature between 500 and 900° C.
 25. The method of claim 16 ,further comprising: repeating the steps of distributing diamondparticles, heating, and cooling until at least a predeterminedpercentage of the exposed surface is diamond.
 26. The method of claim 16, wherein the step of distributing diamond particles comprises:distributing diamond particles having a maximum dimension of less thanor equal to 50 μm.
 27. The method of claim 16 , further comprising:performing chemical vapor deposition to deposit diamond on the exposedsurface.
 28. The method of claim 16 , further comprising: hydrogenatingexposed surfaces of the diamond particles.
 29. The method of claim 16 ,wherein the step of distributing a ceramic binder comprises:distributing ceramic particles made of glass.
 30. The method of claim 16, wherein the step of distributing a ceramic binder comprises:distributing ceramic particles made of porcelain.
 31. The method ofclaim 16 , wherein the steps of distributing a ceramic powder anddistributing diamond particles is performed simultaneously using amixture of said ceramic powder and said diamond particles.
 32. Animplement comprising: a substrate; and a diamond-tiled coating layerformed on said substrate, said coating layer comprising a binder and aplurality of diamond particles bonded to and at least partially embeddedin the binder to provide an exposed diamond-tiled surface.
 33. Theimplement of claim 32 , wherein the binder comprises: a ceramicmaterial.
 34. The implement of claim 32 , wherein the substratecomprises: a material selected from a group consisting of a metal and aceramic.
 35. The implement of claim 34 wherein said substrate comprisesa ceramic material and said binder comprises a ceramic materialintegrally formed with said substrate.
 36. The implement of claim 32 ,wherein at least 40 percent of the exposed surface is diamond.
 37. Theimplement of claim 32 , wherein the diamond particles have a maximumdimension less than or equal to 50 microns and greater than 0.01 μm. 38.The implement of claim 32 , wherein the diamond particles have a maximumdimension less than or equal to 5 microns and greater than 1 micron. 39.The implement of claim 32 , wherein the diamond particles have a maximumdimension less than or equal to 1 micron and greater than 0.01 microns.40. The implement of claim 32 , wherein the diamond particles have amaximum dimension of 0.5 microns.
 41. The implement of claim 32 ,wherein the diamond particles have a maximum dimension less than orequal to 0.01 microns.
 42. A product selected from a group consisting ofa cooking utensil, a grinding device, a lapping device, a polishingdevice, a finishing device, a plumbing fixture, a ski, a skid, a hotpress, a boat hull or other marine article, an electrostatic chuck, abearing, and a sliding electrical contact, utilizing the implementrecited in any one of the claims 32, 34, 37, 39, wherein said productserves as said substrate on which the diamond tiled coating layer isformed.
 43. A product selected from a group consisting of a cookingutensil, a grinding device, a lapping device, a polishing device, afinishing device, a plumbing fixture, a ski, a skid, a hot press, a boathull or other marine article, an electrostatic chuck, a bearing, and asliding electrical contact utilizing the implements recited in any oneof the claims 32, 34, 37, 39, wherein the implement is laminated onto asurface of said product.